There is a device for internal protection of smooth pipe joints and those of flanged pipe connections from aggressive substances within. It includes a sleeve (one or several) installed inside the pipe, and has seals interacting with end surfaces of the internal protective cover or internal lining of the pipe. The sleeve enables to join separate sections of the pipe preventing effect of the pumped medium on the internal surface and, therefore, its corrosion (U.S. Pat. No. 3,235,291, Feb. 15, 1966).
The drawback of this device is narrowing of the pipeline cross-section, complicated nature of the repeated assembly-disassembly of the joint and the need to replace the O-rings.
Use of polymeric coupling (RU 2389943, May 20, 2010) is known for insulation of the pipe joints in polymeric sheath for heat supply networks, water supply systems and oil pipelines. Such coupling, however, is not particularly reliable.
There is a protective device for internal taper thread of pipe couplings of oil pipes grades (RU 2135882, 27, Oct. 1999) in the form of protective flared sleeve of foaming polymer, e.g. of polystyrene. The outer diameter (hereinafter referred to as “OD”) of the sleeve is made larger than the inner diameter (hereinafter referred to as “ID”) of the thread being protected by the value allowing elastic compression of the sleeve material.
By technical essence, the closest is the device providing insulation of the internal surface of the threaded coupling to connect two pipes, including stepped sleeve with the middle section of increased diameter and two end sections with smaller outside diameters installed between the ends of the pipes with tapered thread and connected with the coupling, having O-rings of elastomer plastics located at the sections of the sleeve with smaller diameter (U.S. Pat. No. 5,470,111, Nov. 28, 1995).
The drawback of this device is narrowing of the pipeline flow area near the coupling and unreliable performance of the O-rings installed on the smaller diameter section and interacting with the sealing surfaces in three planes. This device does not compensate wear of the couplings tapered threads at their frequent screwing and unscrewing, which is common during operation of the column tubing strings in oil and gas wells. This leads to seal failure and entering of the aggressive fluid into the gap. Besides, installation of such devices requires individual adjustment of their axial sizes for each separate connection.